1. From the Vascular Biology and Hypertension Branch (Z.S.G.) and the Office of the Director (M.S.L.), Division of Cardiovascular Sciences; the Office of the Director, Division of Blood Diseases and Resources (W.K.H.), and Office of the Director, Division of Lung Diseases (J.P.K.), National Heart, Lung, and Blood Institute of the National Institutes of Health, Bethesda, MD.